Mixtures of cationic and anionic surfactants have potential for use in applications in a wide variety of markets, including in household and personal care product formulations. However, it is known that conventional anionic and cationic surfactants are generally not compatible, tending to precipitate when mixed in aqueous solution. Precipitation is undesirable because it renders the surfactants substantially or completely ineffective. Therefore, anionic and cationic surfactants are difficult to mix without the risk of precipitation or instability.
There have been a number of efforts in the prior art to overcome the problem of instability of cationic-anionic surfactant systems. The prior art efforts, however, exhibit various limitations or are overly complex. For instance, prior art efforts require that one component of the oppositely charged pairs be small in molecular size, or one of the components be weakly charged, or that a co-surfactant/bridging surfactant be used.
It would be a significant advance in the art to provide a cationic/anionic surfactant system that is simple, exhibits favorable properties and that is stable in aqueous solution.